US4436286A - Process of afterburning combustible constituents of exhaust gases from rotary kilns - Google Patents

Process of afterburning combustible constituents of exhaust gases from rotary kilns Download PDF

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Publication number
US4436286A
US4436286A US06/417,956 US41795682A US4436286A US 4436286 A US4436286 A US 4436286A US 41795682 A US41795682 A US 41795682A US 4436286 A US4436286 A US 4436286A
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Prior art keywords
afterburning
oxygen
gas
temperature
stage
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Expired - Fee Related
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US06/417,956
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English (en)
Inventor
Wolfram Schnabel
Ernst Scheu
Harry Serbent
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GEA Group AG
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Metallgesellschaft AG
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Assigned to METALLGESELLSCHAFT AKTIENGESELLSCHAFT, A GERMAN CORP. reassignment METALLGESELLSCHAFT AKTIENGESELLSCHAFT, A GERMAN CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: SCHEU, ERNST, SCHNABEL, WOLFRAM, SERBENT, HARRY
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
    • F27D17/004—Systems for reclaiming waste heat
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/08—Making spongy iron or liquid steel, by direct processes in rotary furnaces
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen

Definitions

  • This invention relates to a process of afterburning combustible constituents of exhaust gases from rotary kilns used for metallurgical processes, wherein the exhaust gases from the rotary kiln are afterburnt in an afterburning chamber supplied with oxygen-containing gases.
  • the exhaust gases from the rotary kiln still contain combustible constituents, which cannot be burned in the rotary kiln.
  • the combustible constituents consist mainly of CO, H 2 , hydrocarbons, solid carbon that has been entrained by the gas or oxidizable products of the process, such as zinc or or lead vapor.
  • the contents of combustible constituents are relatively high if the rotary kiln is charged with coals which have a high content of volatile constituents.
  • the exhaust gases also contain incombustible fine dusts. In order to avoid a pollution of the environment and to utilize the latent heat content of the exhaust gases, their combustible constituents must be afterburnt and the dusts must be removed from the exhaust gas.
  • German No. 20 01 563 It is known from German No. 20 01 563 to provide an exhaust gas duct which has a cooled pipe wall and directly succeeds the gas outlet end of a rotary kiln and opens into the radiant heating space of a waste heat boiler. Shortly before the radiant heating space, oxygen-containing gases are supplied to effect a complete afterburning. Part of the gas which has been completely afterburnt is cooled in the waste heat boiler below the caking temperature of its solid contents and is then withdrawn from the waste boiler and used to heat the charge on a traveling grate. Whereas incrustation can be avoided to a high degree by this practice, a closely succeeding waste heat boiler is always required which involves a considerable expenditure. Additionally, care must be taken to maintain a laminar flow in the radiant heating space in order to prevent an incrustation by softened solids reaching the wall.
  • This object is accomplished, according to the invention, in that part of the combustible constituents is burned in each of a plurality of series-connected stages, each of which is suppled with oxygen at a controlled rate and the gas which is about to enter each succeeding stage is cooled by injected water.
  • Afterburning is effected in at least two stages. If the temperature of the exhaust gas leaving the rotary kiln is close to or at the caking temperature of the entrained fine dust, the gas which is about to enter the first afterburning stage is cooled by injected water. If the temperature of the exhaust gas is below the caking temperature, no cooling is required before the first stage.
  • the caking temperature depends on the composition of the entrained solids. Oxygen is blown into the first afterburning stage only at such a rate that the heat produced by afterburning does not increase the gas temperature above the caking temperature.
  • the gas After the first stage, the gas is cooled by injected water.
  • the gas is treated analogously in the second stage and any further stage. No cooling is required after the last stage.
  • the several stages in the afterburning chamber are not separated by partitions.
  • the afterburning chamber is generally defined by an upright tower, to which supply conduits for the oxygen-containing gas and the water are connected on certain superimposed levels. At critical points where the gases are deflected, cooling surfaces may be incorporated in order to prevent incrustation and to permit a higher heat recovery.
  • the afterburning chamber may also be used as a radiant heating space of a waste heat boiler.
  • the heat content of the afterburnt exhaust gases may be used to preheat feedstock or to produce hot water or steam or electric power.
  • the oxygen-containing gases enter the afterburning chamber with a swirl and for this purpose are tangentially blown into said chamber. This results in a thorough mixing and in a controlled afterburning in each stage.
  • the velocity of the oxygen-containing gases leaving the nozzles is controlled by a variation of the exit cross-section of the nozzles. This ensures a stable combustion even when the gas rates vary because a thorough mixing will always be effected.
  • the oxygen-containing gases are fed into successive afterburning stages with swirls in mutually opposite senses. This will result in a very effective mixing and afterburning of the gases in each stage.
  • the exhaust gases which are about to enter an afterburning stage are cooled to a temperature which is slightly above the ignition temperature of the gases in said stage.
  • the gases are generally adjusted to a temperature of 40° C. to 150° C., especially 50° C. above the ignition temperature. This permits complete afterburning under favorable operating conditions in a few stages.
  • the gas which is about to enter a stage should not be cooled below its ignition temperature.
  • the oxygen-containing gas supplied to the afterburner plant comprises dust-entraining air from locations where coal is unloaded and/or the locations where coal is transferred and/or from a crusher for coal. Removal of dust from such coal environments is normally required for ecological purposes. This removal of dust from such coal environment is effected by sucking air from said locations. The coal-containing air must subsequently be purified. Purification is normally effected in tubular filters or in a gas-purifying electrostatic precipitator. This involves additional costs and involves a risk of coal dust explosions because the dust-entraining air has been sucked off may contain coal dust in a high concentration for short times. Such purification of coal dust entrained air can be avoided if the dust-entraining air is supplied to the afterburning chamber.
  • the advantages afforded by the invention reside in that the gaseous and solid combustible constituents of the exhaust gas can be completely afterburned in a technically satisfactory manner and without incrustation or damge to the lining. A complete afterburning can be effected without need for a high excess of oxygen. The heat content of the exhaust gases can be utilized to a high degree.
  • the annexed drawing shows schematically a cross-section of an afterburner disposed at the feed end of a rotary kiln.
  • the afterburning chamber had a height of 6.4 meters and an inner diameter of 3.5 meters.
  • the waste gas was cooled to a mean temperature of 950° C. by injection of water and then supplied into the first stage of the afterburning chamber.
  • the gas was cooled by injection of water to a mean temperature of 1000° C. ⁇ 50° C. corresponding to the softening behavior of the dust before entrance into the outlet gas duct.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
  • Incineration Of Waste (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Gasification And Melting Of Waste (AREA)
  • Air Supply (AREA)
US06/417,956 1982-03-12 1982-09-14 Process of afterburning combustible constituents of exhaust gases from rotary kilns Expired - Fee Related US4436286A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3208987 1982-03-12
DE19823208987 DE3208987A1 (de) 1982-03-12 1982-03-12 Verfahren zur nachverbrennung von brennbaren bestandteilen in abgasen von drehrohroefen

Publications (1)

Publication Number Publication Date
US4436286A true US4436286A (en) 1984-03-13

Family

ID=6158047

Family Applications (1)

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US06/417,956 Expired - Fee Related US4436286A (en) 1982-03-12 1982-09-14 Process of afterburning combustible constituents of exhaust gases from rotary kilns

Country Status (11)

Country Link
US (1) US4436286A (xx)
EP (1) EP0089075B1 (xx)
AU (1) AU556563B2 (xx)
CA (1) CA1206751A (xx)
DE (2) DE3208987A1 (xx)
IN (1) IN157095B (xx)
MY (1) MY8700258A (xx)
NO (1) NO157942C (xx)
NZ (1) NZ203438A (xx)
PH (1) PH19731A (xx)
ZA (1) ZA831679B (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4762884A (en) * 1986-04-24 1988-08-09 Bayer Aktiengesellschaft Process for the production of radiation-crosslinked thermoplastic polyurethanes
US6547848B1 (en) 1999-05-26 2003-04-15 Outokumpu Oyj Method for cooling the gas flow in a smelting furnace

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4339591A1 (de) * 1993-11-20 1995-05-24 Metallgesellschaft Ag Wälzverfahren zur Aufarbeitung von Zink, Blei und Eisenoxide enthaltenden Materialien

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1039084B (de) * 1953-04-30 1958-09-18 Waagner Biro Ag Verfahren und Einrichtung zur fortlaufenden Ausnuetzung der absatzweise anfallenden Waermemenge von Konverterabgasen
FR1259048A (fr) * 1960-03-11 1961-04-21 Renault Procédé et dispositif pour la préparation de protoxyde de fer
US3157228A (en) * 1961-09-01 1964-11-17 Hazen Engineering Company Apparatus for cooling metal recuperator gases
DE2001563C3 (de) * 1970-01-15 1979-05-17 Metallgesellschaft Ag, 6000 Frankfurt Drehrohrofen zur thermischen Behandlung von Feststoffen und Verfahren zum Betreiben des Drehrohrofens
DE2005220A1 (en) * 1970-02-05 1971-08-19 Weissheimer V Metallurgical furnace flue gas removal plant
DE2437245C3 (de) * 1974-08-02 1979-01-18 Demag Ag, 4100 Duisburg Vorrichtung zur kontrollierbaren Rauchgasverbrennung für einen geschlossenen Lichtbogen-Reduktionsofen zur Erzeugung von Metallen und Metall-Legierungen '
US4040819A (en) * 1976-08-06 1977-08-09 Rounds Gerald L Basic oxygen steel furnace and process

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4762884A (en) * 1986-04-24 1988-08-09 Bayer Aktiengesellschaft Process for the production of radiation-crosslinked thermoplastic polyurethanes
US6547848B1 (en) 1999-05-26 2003-04-15 Outokumpu Oyj Method for cooling the gas flow in a smelting furnace

Also Published As

Publication number Publication date
PH19731A (en) 1986-06-17
ZA831679B (en) 1984-10-31
EP0089075A1 (de) 1983-09-21
EP0089075B1 (de) 1985-09-25
CA1206751A (en) 1986-07-02
NO157942B (no) 1988-03-07
NZ203438A (en) 1985-08-16
NO830751L (no) 1983-09-13
AU556563B2 (en) 1986-11-06
AU1242583A (en) 1983-09-15
MY8700258A (en) 1987-12-31
IN157095B (xx) 1986-01-11
NO157942C (no) 1988-06-15
DE3360855D1 (en) 1985-10-31
DE3208987A1 (de) 1983-10-27

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